The present invention relates to an endoscope, and more specifically to an endoscope having an insertion section formed of a multi-lumen tube.
Recently, in order to make the insertion section small in diameter, there have been endoscopes developed whose insertion section is formed of a multi-lumen tube, which has a small diameter. The multi-lumen tube includes a solid tube member of flexible resin, having a plurality of insertion channels extending in its axial direction. The tube member serves directly as the insertion section. An image guide fiber, light guide fiber, etc., are inserted individually in the channels.
In general, an objective optical system and an illuminating optical system are disposed in the distal end portion of the insertion section. Since the insertion section, formed of the multi-lumen tube, is flexible, its distal end portion can be deformed by the load of the optical systems therein. Accordingly, the optical systems may possibly become eccentric to the image guide fiber or light guide fiber, or their optical axes may incline at some angle to the central axis of the image or light guide fiber. In such cases, the optical systems cannot function well.
Moreover, resin is exposed from the distal end portion of the insertion section. Therefore, if a laser probe is passed through one of the channels, and if a laser beam is radiated from the distal end of the insertion section, the distal end portion will be burned by the laser beam reflected by an irradiated region of a subject's body.